Within 2-3 days SOC dropped from 90% to 7%

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Sveinung L. Johansen asked Nov 11, '20

Within 2-3 days SOC dropped from 90% to 7%

Hi,
As you can see from the attached graph SOC dropped from 90% to 7% in the span of 2-3 days.  The system has been up and running since June and nothing like this have happened before. The consumption has been more or less constant for a long time (25W) and the only thing that draws power directly from the battery is the CCGX.

Could this drop be a result of some “maintenance” routine initiated from the CCGX or the BYD BMU/BMS?

The system consists of the following components:

•Color Control GX
•MultiPlus-II 48/5000/70-48
•BYD B-Box Pro 7.5
•SmartSolar Charger MPPT 250/60
•
Regards
Sveinung

Lithium Battery CCGX Color Control SOC BYD

1605094160988.png (55.1 KiB)

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Guy Stewart (Victron Community Manager) answered · Nov 11, 2020 at 12:03 PM

Hi @Sveinung,

This model of batteries have an issue where they are not very good at measuring very low power demand, anything less than 50W ~1A per module is not very reliable - this is explained a bit more in the BYD Victron integration guide here.

This is not normally an issue if the battery is recharging to 100% - 55.1+ V. At that voltage, it will recalibrate the SOC reading.

It seems like something has changed in that time that meant the battery was no longer reaching that 'recalibration' voltage threshold.

I can only speculate why that might be the case, but that is surely the explanation for inexplicable SOC drop.

PS you have my curiosity for why have this considerable power system seemingly doing no work, and connected to no loads (except the monitoring)?

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Sveinung L. Johansen commented · Nov 11, 2020 at 12:52 PM

Hi,

Thank you that explains it :)

This is an off-grid system up in the mountains in Norway and at this time of the year the road is closed and the cottage is not in use. The only thing that draws power is a 4G router, WEB cam base station and a 220v - 12v inverter for a remotly controlled paraffin oven.

This is how it looks today:

and the installation:

BR

Sveinung

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Sveinung L. Johansen commented · Nov 17, 2020 at 06:14 AM

Hi,

Then it happened again and this time the system shut down. My question is will the batteries survive the winter with voltage as low as 48.5V? Might take a couple of months before I’m able to get up there again.

/Sveinung

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1605593642246.png (103.3 KiB)

Modifications Space

Node Red Space

Answer 1 · 2020-11-11T12:51:45Z

JohnC answered · Nov 11, 2020 at 12:51 PM

Hi @Sveinung

I'm curious too. You have some other load in your system that isn't showing on that graph. My system does the same, seemingly anything that doesn't go through the Multi, like dc loads, doesn't make it onto that chart. Even with a Smartshunt (in my case), it doesn't show.

And you have some relatively massive solar days compared to your graphed usage, that isn't reflected in a rise in the SOC reading.

Something else seems to be happening. Where's that energy going?

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